Flexible hoses are used to transfer fluid from one place to another and common applications are for transferring water, pressurised air, hydraulic fluid or any other fluid from one piece of equipment to another. Usually, fluid at one end of the hose is pressurised, possibly by a pump or header tank, and each end of the hose is provided with a connector that sealably connects the hose to the equipment. It is known to provide a hose for connecting one aircraft to another for the purpose of in-flight refuelling.
In-flight refuelling systems involve moving aviation fuel from a tanker aircraft to a receiving aircraft to increase the operating range and time of the receiving aircraft by overcoming the maximum fuel load limitation.
Currently, there are two main known methods of in-flight refuelling—‘probe and drogue’ and ‘flying boom’. The probe and drogue arrangement involves a flexible hose with a valve and a drogue at the distal end of the hose. The hose is extended from the tanker aircraft and is pulled behind the tanker aircraft by the aerodynamic force created by the drogue, which also provides some positional stability. The receiving aircraft comprises a probe extending forwardly from the nose or fuselage of the aircraft, and also has a valve at its distal end. The pilot of the aircraft to be refuelled controls and manoeuvres the aircraft to align the probe with the valve and the drogue and then moves the aircraft towards the tanker aircraft so that the probe connects with the valve on the hose. Once connection has been made, the valves can be opened to establish a fluid path, thereby allowing fuel to flow into the fuel tanks of the receiving aircraft.
Flying boom refuelling systems have a rigid boom that is deployed from the tanker aircraft, the position of which is typically controlled by an operator in the tanker aircraft. The boom can carry a hose which has a valve at its distal end. The receiving aircraft comprises a docking port that may be within the fuselage, or extending from the fuselage. The pilot of the receiving aircraft again flies their aircraft into contact with the boom. However, in this case, the boom operator can control the finite position of the boom so there is a two-way process for making the connection.
Developments in aviation mean that the industry is changing to favour Unmanned Aerial Vehicles (UAV's) and Autonomous Unmanned Aerial Vehicles (AUAV's) and the refuelling requirements of these aircraft are very different to those of conventional aircraft. A limitation of UAV's and AUAV's is the power that can be carried by onboard batteries which are recharged before each use.
Aircraft currently communicate via radio or satellite communications which can place a large strain on the bandwidth of such systems. UAV's and AUAV's that are deployed as observers can collect and store large amounts of data that is either transmitted over the communication channels or stored onboard the aircraft for later retrieval. Transmission over the communication channels requires more bandwidth which means more satellites, transmitters and receivers that can add considerable cost. Furthermore, communication channels may not he fast or secure enough to carry out some operations such as system diagnostics. Storing data onboard the aircraft delays the retrieval of that information and requires the aircraft to return to the ground. Therefore, the data storage capacity of an aircraft may also limit the aircraft's maximum operational time.